Total average power loss is the significant component in the overall power loss of a switching power supply and is estimated at 35% to 40%. The Total average power loss has an adverse impact on the performance of the switching power supply, by reducing efficiency and reliability, and by causing an increase in the size of the needed heat sink.
In order to know the exact impact, it is important to measure and characterize the total average power loss, switching loss at the switching device. Unfortunately, there are no currently available test tools in market to measure total average power loss or to measure switching loss in time varying signals.
Total average and switching loss at a switching device is currently analyzed by two methods: Thermal, and Manual. The Thermal technique has following limitations and difficulties. The design engineer needs stimuli to excite the switching device with proper voltage and current. It is time consuming, prone to human error, and the design engineer cannot isolate power loss components such as Ton loss, Toff loss, and conduction loss.
The second method uses a Digital Storage Oscilloscope (DSO) and a Manual measurement technique. This measurement technique has following limitations and difficulties. It, too, is time consuming. It, too cannot separately measure Ton time loss or Toff time loss. Moreover, it is not possible to make measurements when the duty cycle and frequency of switching cycle are varying.
Because of this complexity in measurement, most of the time, designers over-design the Switch Mode Power Supply (SMPS) resulting in lower efficiency and higher cost.
What is needed is an automated method of measuring Total average power loss, and switching loss using a digital storage oscilloscope. This technique of measurement can be applied to switching power supplies that are used in the Computer, Communication, Automotive, and Electronic Ballast industries, thereby overcoming the above-described limitations of thermal and manual computation.